Pressure differential indicating means

ABSTRACT

THIS INVENTION RELATES TO EQUIPMENT FOR INDICATING A PREDETERMINED PRESSURE DIFFERENTIAL BETWEEN GASEOUS FLUIDS AT LOW AND HIGHER PRESSURES. A HOLLOW SLEEVE OF CONICAL FORM HAS AN INNER TAPERED WALL. THE LARGE END OF THE HOLLOW SLEEVE IS IN COMMUNICATION WITH THE GASEOUS FLUID AT THE HIGHER PRESSURE AND ITS SMALL END IS IN COMMUNICATION WITH THE GASESOUS FLUID AT THE LOW PRESSURE. A MOVABLE MEMBER OF CONICAL FORM, WHICH HAS A TAPERED OUTER WALL, IS DISPOSED WITHIN THE HOLLOW SLEEVE WITH THE SMALL END OF THE MEMBER AT THE SMALL END OF THE SLEEVE. THE MEMBER, WHICH IS SPRING BIASED FROM THE SMALL END OF THE SLEEVE, HAS A SIGNALLING SYSTEM PART MOUNTED THEREON. THE PART AND MEMBER ARE IN ONE POSITION WITH RESPECT TO THE SLEEVE WHEN THE PRESSURE DIFFERENTIAL BETWEEN THE GASEOUS FLUIDS IS LESS THAN A PREDETERMINED VALUE AND IN A SECOND POSITION WITH RESPECT TO THE SLEEVE WHEN THE PRESSURE DIFFERENTIAL BETWEEN THE GASEOUS FLUIDS IS AT THE PREDETERMINED VALUE. THE RELATIVE POSITION OF THE PART AND MEMBER WITH RESPECT TO THE SLEEVE IS DEPENDENT UPON THE VELOCITY OF AIR FLOWING FROM THE LARGE TO THE SMALL END OF THE SLEEVE THROUGH A GAP BETWEEN THE SLEEVE AND MEMBER. THE PART IN ITS SECOND POSITION SIGNALS THAT THE PRESSURE DIFFERENTIAL BETWEEN THE GASEOUS FLUIDS IS AT THE PREDETERMINED VALUE.

United States Patent [72] inventor ErfiAmeAldenen 3,119,369 1/1964Harland etal. 116/114 Ihgersten, Sweden 3,381,652 5/1968 Schaefer et al.116/114 [211 App]. No. 857,502 3,443,365 5/1969 Lee et al. 55/274 filed1969 Primary Examiner-Louis J. Capozi Patent! Alto EdmundA Fenander mAssignee AktieholagetEleetrolnx Stockholm, Sweden Pnomy 1968 ABSTRACT:This invention relates to equipment for indicat- [33] i ing apredetermined pressure difl'erential between aseous 31 8 i 500/1968fluids at low and higher pressures. A hollow sleeve of conical form hasan inner tapered wall. The large end of the hollow Essn "MERE sleeve isin communication with the gaseous fluid at the higher [54] n I LINDICATING MEANS pressure and its small end is in communication with thegaseous fluid at the low pressure. A movable member of conical [52] US."116/70, form, which has a tapered outer wall, is disposed within the15/339, 551274, 73/208, 116/70, 116/114, hollow sleeve with the smallend of the member at the small 21 0 end of the sleeve. The member, whichis spring biased from [51] Int. Cl (101119/12 he small and of thesleeve, has a signaling system part FieldotSeareh 116/65, 70, nt dthereon. The part and member are in one position with respect to thesleeve when the pressure differential l 7/( q i /2 274 between thegaseous fluids is less than a predetermined value and in a secondposition with respect to the sleeve when the [56] Refenum Cited pressuredifferential between the gaseous fluids is at the UNITED STATES PATENTSpredetermined value. The relative position of the part and 2,136,26111/1938 Anderson 116/117X member with respect to the sleeve is dependentupon the ,192,224 3/1940 Forsberg 116/1 14X velocity of air flowing fromthe large to the small end of the 2,244,552 6/1941 DeLaney.. 73/203sleeve through a gap between the sleeve and member. The 2,325,188 7/1943 l..ofgren.... 55/274 part in its second position signals that thepressure differential 2,327,181 8/ 1943 Dunbar 1 16/1 14X etween h g efluids is a he predetermined value.

b 205 2/ 2 K 25 /5b a Q 11 11111111: 22 f /0 L #61 /9 /5a./,l'l/////////// /1 /5 PRESSURE DIFFERENTIAL INDICATING MEANS SUMMARY OFTHE INVENTION It is an object of my invention to provide an improvedmeans for indicating a predetermined pressure differential betweengaseous fluids at low and higher pressures. l accomplish this byproviding indicating means comprising a hollow sleeve of conical formwhich has an inner tapered wall and a movable member of conical formwhich is disposed within the hollow sleeve and has a tapered outer wall.The small and large ends of the movable member are respectively at thesmall and large ends of the sleeve. The small and large ends of thehollow sleeve are respectively in communication with the gaseous fluidsat the low and higher pressures.

Further, the movable member is biased from the small end of the sleeveand has a part thereon which forms a component of a signaling system.The part and member are in one position with respect to the sleeve whenthe pressure differential between'the gaseous fluids is less than apredetermined value and in a second position with respect to the sleevewhen the pressure differential between the gaseous fluids at least atthe predetermined value. The relative position of the part and memberwith respect to the sleeve is dependent upon the velocity of air flowingfrom the large to the small and of the sleeve through a gap between thesleeve and member.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, the single figure isa fragmentary sectional view of apparatus which has a space maintainedat a vacuum and is provided with pressure differential indicating meansembodying my invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, I haveshown my invention as applied to apparatus having a casing 11 providedwith a space or chamber 12 which is maintained at a vacuum orsubatmospheric pressure in any suitable manner. In apparatus of the kindbeing described. such as a vacuum cleaner, for example, it is desirableto employ means to indicate when the vacuum or subatmospheric pressurein the chamber 12 reaches a predetermined pressure below atmosphericpres- I sure.

In accordance with my invention I provide a pressure differentialindicating means 14 for indicating a predetermined pressure differentialbetween atmospheric pressure and the vacuum or subatmospheric pressureproduced in the chamber 12. The indicating means 14 is disposed withinthe casing 11 and includes a stationary hollow sleeve or cylinder 15 ofconical form having a tapered inner wall 15a. The large end 15b of theconical sleeve 15 extends to and is closed off by a removably securedwall part 11a of the casing 11 which has an opening 16 so that the endllSb of the conical sleeve 15 is in communication with ambient air atatmospheric pressure.

The small end 150 of the stationary conical sleeve 15 is incommunication with a chamber 17 which is adjacent to the chamber 12 andseparated therefrom by a partition 18 having an opening 19. Hence, thesmall end 15c of the conical sleeve is in communication with air in thechamber 17 which is at the vacuum or subatmospheric pressure maintainedin the chamber 12.

A movable member or piston 20 of conical form, which has a tapered outerwall 20a of generally the same configuration as the inner wall 150 ofthe stationary sleeve is axially positioned within the sleeve 15, andmovable therein in its lengthwise direction. The piston 20 is hollowwith its large open end 200' near the wall part 11a of the casing 11 inwhich the opening 16 is provided. The piston 20 is resiliently biasedtoward the right in the drawing by a helical spring 21, one end of whichis fixed to the small closed end 20b of the piston and the opposite endof which is fixed to a screw 22 extending through the wall part 11a ofthe casing 11, so that the biasing action of the spring 21 can readilybe adjusted.

A vertical arm 23a of an L-shaped part 23 is fixed to the closed end 20bof the conical piston 20, the horizontal arm 23b of which is movablethrough slots 24 into and from the interior 25 of a hollow body 26anchored in an opening 27 in the top wall 11b of the casing 11. The body26 us provided with a top wall 26a formed of transparent material. Thebottom wall 26b of the body 26 and the horizontal arm 23b of theL-shaped part 23, which is flat and overlies the bottom wall 26b of thebody 26 in its dotted line position in the drawing, are colored. Forexample, the bottom wall 26b of the body 26 can be colored green and theflat horizontal arm 23b of the L-shaped part 23 can be colored red.

When the L-shaped part 23 is in its solid line position in the drawing,the flat horizontal arm 23b thereof is outside the body 26 and hence thegreen colored bottom 26b of the body will be visible through thetransparent top wall 26a thereof. When the L-shaped part 23 is in itsdotted line position in the drawing, the flat horizontal arrn 23bthereof is in the interior 25 of the body 26 and the red colored flathorizontal arm 23);. of the L-shaped part 23 will be visible through thetransparent top wall 26a of the body 26.

The conical piston 20, L-shaped part 23 and hollow body 26 all can beformed of suitable plastic material. By making the conical piston 20 ofplastic material having a relatively thin wall 20, the weight of themovable element of the indicating means 14 will be very low and nospecial provision will be necessary to center the conical piston withinthe stationary sleeve 15, as will be explained presently, to maintain agap 28 between the sleeve and piston which is of substantially uniformwidth about the entire periphery of the piston. Although not shown, italso will be understood that the piston 20 can be provided with asuitable bearing movable lengthwise of an elongated pin supported in anysuitable manner within the hollow sleeve 15, so that the piston 20 willbe centered within the sleeve.

When a vacuum or subatmospheric pressure is maintained in the chamber 12during operation of the apparatus 10, ambient air at atmosphericpressure will enter the large end 15b of the hollow sleeve 15 throughthe opening 16 in the wall part Ila due to the fact that the chamber 17which is in communication with the chamber 12 through the opening 19 inthe partition 18, also is at a vacuum or subatmospheric pressure. Underthese conditions ambient air entering the large end of the conicalsleeve 15 will flow through the gap 28 into the chamber 17.

When the pressure differential between 'the ambient air and air in thechamber 17 is less than a predetermined value, the

piston 20 will move to a position within the hollow sleeve at which thewidth of the gap 28 is in the neighborhood of about is to l mm., forexample. This position of the piston 24 which tends to move toward theleft in the drawing with flow of air from right to left through the gap28, is counteracted by the biasing action of the spring 21. The airflowing through the gap 28, which is of annular form and is disposedabout the entire periphery of the piston 20, functions to center thepiston 20 axially of the sleeve 15 and maintain the width of the gap 28substantially the same about the piston.

When the pressure differential between the ambient air and air in thechamber 17 is at a predetermined value, the air flowing through the gap28 from the large end 15b to the small end of the sleeve 15 will impartmovement to the piston 20 and the latter will move toward the small end15c of the sleeve 15. An important operating feature of the indicatingmeans 14 is that, under conditions where such movement imparted to thepiston 20 is very small and not very great, such slight movement of thepiston 20 toward the left in the drawing will decrease the width of thegap 28 due to the fact that the sleeve 15 and piston 20 are of conicalform. Such decrease in the width of the gap 28 in turn will cause theair to flow through the gap 28 at a higher velocity toward the small end15c of the sleeve 15. This in turn imparts more movement to the piston20 and the latter moves further toward the small end 150 of the sleeve15. The successive increases in velocity of the air through the gapZ8Jand the successive increments of movement imparted to the piston 20take place very fast so that, when initial movement is imparted to thepiston 20 responsive to a predetermined pressure difference betweenambient air at atmospheric pressure and air at vacuum or subatmosphericpressure in chamber 12, the piston 20 moves quickly practically in 'asingle stroke to shift the closed end 20a of the piston 20 from itssolid to its dotted line position in the drawing. when this occurs thegreen colored bottom 26b of the body 26 no longer will be visiblethrough the transparent top wall 26a thereof and only the red-coloredflat horizontal arm 23b of the L-shaped part 23 will be seen through thetransparent top wall 26a.

in view of the foregoing, it will now be understood that the horizontalflat arm 23b of the L-shaped part 23 shifts quickly from its solid toits dotted line position in the drawing when the pressure differentialbetween the ambient air at atmospheric pressure and the air at a vacuumor subatmospheric pressure is at a predetermined value, thus giving apositive indication that this operating condition has occurred. Further,the parts of the pressure differential indicating means 14 are sorelated to one another that a relatively long path of movement isprovided for the piston 20 to shift the flat horizontal arm 23!) fromits solid line to its dotted line position in the drawing, so thatmalfunctioning can never occur.

The relative position of the L-shaped part 23 and member 20 with respectto the sleeve 15 is dependent, as pointed out above, upon the velocityof air flowing from the large end 15b to the small end 15c of the sleevethrough the gap 28 between the sleeve 15 and member 20. The part 23 andmember are in the solid line position in the drawing with respect to thesleeve 15 when the pressure differential between ambient air andsubatmospheric air in chamber 12 is less than a predeter mined valueandin the dotted line position in the drawing with respect to the sleevewhen the pressure differential between ambient air and subatmosphericair in the chamber 12 is at the predetermined value. The part 23 in itsdotted line position in the drawing, as explained above, signals thatthe pressure differential between ambient air and air in the chamber 12is at the predetermined value.

lclaim:

1. Means for indicating a predetermined pressure differential between afirst gaseous fluid at a first pressure and a second gaseous fluid at asecond lower pressure, said indicating means comprising:

a. a hollow sleeve having an inner tapered wall surface of conical form,the large end of said hollow sleeve being in communication with thefirst gaseous fluid at the first pressure and the small end thereofbeing in communication with the second gaseous fluid at the second lowerpressure;

b. an elongated member having a tapered outer surface of conical form,said member being disposed within said hollow sleeve and axially movabletherein with the small and large ends thereof respectively at the smalland large ends of said sleeve;

c. said hollow sleeve and said member having spaced inner and outersurfaces, respectively, defining a gap therebetween which is of conicalform and through which gaseous fluid flows from the large end to thesmall end of said sleeve; signal means;

e. means including said member in a first axial position within saidsleeve to render said signal means ineffective and in a second axialposition within said sleeve, which is nearer to the small end thereof,to render said signal means effective; said member being axially movablewithin said sleeve to said first position responsive to a pressuredifferential between the first and second gaseous fluids which is lessthan a predetermined value; g. said member being axially movable withinsaid sleeve to said second position responsive to a pressuredifferential between the first and second gaseous fluids which is atleast at the predetermined value; and

h. said member, when movement thereof is initiated from its firstposition to its second position responsive to a pressure differentialbetween the first and second gaseous fluids which is at least at thepredetermined value, functioning to decrease the width of said gap dueto the conical from of said hollow sleeve and said member, whereby thevelocity of the gaseous fluid flowing through-said gap from the largeend to the small end'of said hollow sleeve will increase rapidly insmall increments and promote movement of said member practically in asingle stroke to its second position and positively render said signalmeans effective when the pressure differential between the first andsecond gaseous fluids is at least at the predetermined value.

2. Indicating means as set forth in claim 1 in which said gap betweensaid hollow sleeve and said member, when said member is in said firstaxial position within said sleeve, is in a range of from A to 3 mm.

3. Indicating means as set forth in claim 1 which includes structuretending to restrain movement of said member from said first axialposition to said second axial position within said sleeve.

4. indicating means as set forth in claim 3 in which said restrainingstructure comprises resilient means for biasing said member from thesmall end toward the large end of said sleeve.

5. Indicating means as set forth in claim 1 in which said membercomprises a hollow cone section formed of lightweight material, such asplastic, for example, having a thin wall, the small end of said conesection being closed and serving as the small end of said member.

6. Indicating means as set forth in claim 5 which includes elongatedspring means for resiliently biasing said hollow cone section from thesmall end toward the large end of said sleeve, said spring meansextending axially within said hollow cone section and having one endfixed to the closed end thereof.

7. Indicating means as set forth in claim 1 in which said signal meansincludes a visual indicator and means hiding said visual indicator fromview when said member is in said first position within said sleeve, saidhiding means being ineffective when said member is in its secondposition within said sleeve whereby said visual indicator is visible tosignal that the pressure differential between the first and secondgaseous fluids is at least at the predetermined value.

8. indicating means as set forth in claim 7 in which said signal meansincludes a transparent sight element, said visual indicator in saidsecond position of said member within said sleeve being visible throughsaid sight element and hidden from view by said hiding means in saidfirst position of said member within said sleeve.

9. Means for indicating a predetermined pressure differential betweenambient air at atmospheric pressure and air at a vacuum orsubatmospheric pressure, as in that part of the path of flow of air in avacuum cleaner which is between the dust bag and motor-fan unit, forexample, said indicating means comprising:

a. a hollow sleeve having an inner tapered wall surface of conical form,the large end of said hollow sleeve being in communication with ambientair and the small end thereof being in communication with air atsubatmospheric pressure;

b. an elongated member having a tapered outer surface of conical form,said member being disposed within said hollow sleeve and axially movabletherein with the small and large ends thereof respectively at the smalland large ends of said sleeve;

c. means for resiliently biasing said member from the small end towardthe large end of said sleeve;

d. said hollow sleeve and said member having spaced inner and outersurfaces, respectively, defining a gap therebetween which is of conicalform and through which air flows from the large end to the small end ofsaid sleeve;

. signal means;

means including said member in a first axial position within said sleeveto render said signal means ineffective and in a second axial positionwithin said sleeve, which is nearer to the small end thereof, to rendersaid signal means effective;

said member being axially movable within said sleeve to said firstposition responsive to a pressure differential between ambient air andair at subatmospheric pressure which is less than a predetermined value;

. said member'being axially movable within said sleeve to said secondposition responsive to a pressure differential between ambient air andair at subatmospheric pressure which is at least at the predeterminedvalue; and

. said member, when movement thereof is initiated from its firstposition to its second position to responsive to a pressure differentialbetween ambient air and air at subatmospheric pressure which is at leastat the predetermined value, functioning to decrease the width of saidgap due to the conical form of said hollow sleeve and said member,whereby the velocity of air flowing through said gap from the large endto the small end of said hollow sleeve will increase rapidly in smallincrements and promote movement of said member practically in a singlestroke to its second position and positively render said signal meanseffective when the pressure differential between ambient air and air atsubatmospheric pressure is at least at the predetermined value.

10. Apparatus comprising:

a. structure defining a first space for holding a body of air maintainedat a vacuum or subatmospheric pressure, such as in a vacuum cleaner, forexample,

b. said structure including wall means defining a second space forholding a body of air in communication with the air in said first space;

c. means for indicating a predetermined pressure differential betweenambient air enveloping the apparatus and air in said first space, saidindicating means comprismg:

d. a hollow sleeve having an inner tapered wall surface of conical form,the large end of said hollow sleeve being in communication with ambientair enveloping the apparatus and the small end thereof being disposed insaid second space and in communication with air at subatmosphericpressure therein;

. an elongated member having a tapered outer surface of conical form,said member being disposed within said hollow sleeve and axially movabletherein with the small and large ends thereof respectively at the smalland large ends of said sleeve;

said hollow sleeve and said member having spaced inner and outersurfaces; respectively, defining a gap therebetween which is of conicalform and through which air flows from the large end to the small end ofsaid sleeve;

means for resiliently biasing said member from the small end toward thelarge end of said sleeve,

. signal means; means including said member in a first axial positionsaid member being axially movable within said sleeve to said firstposition responsive to a pressure differential between ambient air andair at subatmospheric pressure which is less than a predetermined value;

. said member being axially movable within said sleeve to said secondposition responsive to a pressure differential between ambient air andair at subatmospheric pressure which is at least at the predeterminedvalue,

. said member, when movement thereof is initiated from its firstposition to its second position responsive to a pressure differentialbetween ambient air and air at subatmospheric pressure which is at leastat the predetermined value, functioning to decrease the width of saidgap due to the conical form of said hollow sleeve and said member,whereby the velocity of air flowing through said gap from the large endto the small end of said hollow sleeve will increase rapidly in smallincrements and promote movement of said member practically in a singlestroke to its second position and positively render said signal meanseffective when the pressure differential between ambient air and air atsubatmospheric pressure is at least at the predetermined value.

